Solenergi på Kvarnholmen
In recent years it has become more and more evident that man has contributed to much of the climate changes that have taken place during the last century. A major challenge today is to reduce emissions and energy usage at the same time as the global population is growing. To contribute to a better environment, Stockholms Stad has set at target of becoming fossil fuel free by the year of 2050. The construction of new districts is done with this goal in mind; energy efficiency and renewable energy sources are examples of methods to achieve this.Solar energy is considered to be a sustainable energy source and the most common techniques to harvest solar energy in Sweden are solar cells and solar collectors which produce electricity and heat respectively. This report aims to investigate whether an investment in any of these systems would prove to be economically beneficial at Kvarnholmen, a district under construction in eastern Nacka, Stockholm.Since the finished blueprints only cover a small portion of Kvarnholmen, the report examines the possibilities for a house where construction has already begun, Nya Kvarnen. Using these calculations, the potential for the rest of the island is estimated based on the vision that was set up in 2005.A model for the sizing of the solar collector system and photovoltaic system on flat roofs was developed as the basis for the subsequent economic calculations. It was based on the orientation of the solar panels or solar collectors, the expected energy production and the estimated demand for hot water and electricity respectively.The economic calculation demonstrates that both solar collectors and PV cells are expected to be beneficial in the dimensions that have been chosen. For the collectors the calculated internal rate of return was 6.9 percent and a total investment cost of SEK 22 million gives a net profit of SEK 30 million after 25 years. The corresponding figures for the PV system are 10 percent internal rate of return, SEK 7.3 million in investment cost and SEK 18 million in net profit for the same life length. The solar collectors produce a total of 1 000 MWh of heat and the solar cells produce a total of 450 MWh electricity during a year. The produced energy is sufficient to cover the whole demand of domestic hot water during June or 60 percent of the electricity required by fridge, freezer and electronics in standby mode during the same month.The conclusion of the calculations and sensitivity analysis is that an investment in any of these systems is likely to be profitable despite the fact that many projects run over budget. The environmental gain in terms of spared carbon dioxide emissions, compared to production of district heating or grid electricity, is about 10 000 tonnes for each system and should be considered when thinking about a possible investment.